Lenticular lens sheet

Abstract

A lenticular lens sheet 4 comprises a plurality of lens elements of incidence 21 arranged on the incidence side, and a plurality of lens elements of emergence 22 arranged on the emergence side. The light that has passed through each lens element of incidence 21 converges via the protruding apex of the corresponding lens element of emergence 22. The lens plane of the center portion C of each lens element of emergence 22, the width of this portion C being a half of the total lens width L (i.e., L / 2), is in the shape defined by a curved line fulfilling the conditions expressed by the following numerical formulae (1) to (4), and the lens plane of each side portion S of each lens element of emergence 22, the width of this portion S being a quarter of the total lens width L (i.e., L / 4), is in the shape defined by a curved line fulfilling the conditions expressed by the following numerical formulae (5) to (8): y=a×b−x−e (−L / 4≦x≦0) . . . (1), y=a×bx−e (0≦x≦L / 4) . . . (2), 3.0×10−4<a<3.8×10−4 . . . (3), 1.0×1024<b<1.0×1025 . . . (4), y=c×d−x−e (−L / 2≦x≦−L / 4) . . . (5), y=c×dx−e (L / 4≦x≦L / 2) . . . (6), 3.0×10−3<c<3.1×10−3 . . . (7), and 2.7×109<d<4.0×109 . . . (8).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a lenticular lens sheet for use in a rear projection screen that allows light emitted from an image source, incident on the rear of the screen, to emerge toward the viewer's side, and more particularly to a lenticular lens sheet capable of reducing the color shift.[0003]2. Description of Related Art A method in which imaging light emitted from three CRT's (projection tubes) for R, G and B, serving as an image source, are magnified by projection lenses and are projected on a rear projection screen (hereinafter sometimes abbreviated to a “screen”) is known as a method of displaying an image on a large-sized screen.[0004]Specifically, for example, in such a rear projection display 10 as is shown in FIG. 1, imaging light emitted from three CRT's 1 for R, G and B, serving as an image source, are magnified by respective projection lenses 2 and are projected on the plane of a rear projection sc...

AI Technical Summary

Benefits of technology

[0008]The inventors have made earnest studies under these circumstances, and, as a result, have found that the shape of lens elements of emergence to be arranged on the emergence side of a lenticular lens sheet is of great importance and that by controlling this shape, it is possible to decrease both the amount of outgoing blue light (B), which has so far appeared to be too large when the projected image is viewed from an angle between 20° and 40°, and the amount of outgoing red light (R), which has so far appeared to be too large when the projected image is viewed from an angle between −20° and −40°.

[0011]According to the first aspect for fulfilling the object of the present invention, in each lens element of emergence through which the light collected by each lens element of incidence passes, the shape of the lens plane of the center portion of the lens, the width of this portion being a half of the total lens width, is different from the shape of the lens plane of each side portion of the lens, the width of this portion being a quarter of the total lens width, and the shapes of the lens planes of these portions are defined by curved lines fulfilling the conditions expressed by the above numerical formulae (1) to (8), so that it is possible to effectively scatter the amount of the light (red light (R) and blue light (B)) that emerge from the lens elements of emergence after obliquely entering the lens planes of these lens elements. For this reason, it is possible to decrease both the amount of outgoing blue light (B), which has so far appeared to be too large when the projected image is viewed from an angle between 20° and 40°, and the amount of the outgoing red light (R), which has so far appeared to be too large when the projected image is viewed from an angle between −20° and −40°. As a result, the balance between those parts in which the amount of light is too large and those parts in which the amount of light is small is improved, and the color shift can thus be reduced.

[0013]According to the second aspect for fulfilling the object of the present invention, in each lens element of emergence through which the light collected by each lens element of incidence passes, the shape of the lens plane of the center portion of the lens, the width of this portion being a half of the total lens width, is different from the shape of the lens plane of each side portion of the lens, the width of this portion being a quarter of the total lens width, and the shapes of the lens planes of these portions are defined by curved lines fulfilling the conditions expressed by the above numerical formulae (1) to (4) and (9) to (12), so that the lens plane of each lens element of emergence can totally reflect not more than approximately 5% of the red light (R) and blue light (B) obliquely incident on the lens plane. For this reason, it is possible to decrease both the amount of outgoing blue light (B), which has so far appeared to be too large when the projected image is viewed from an angle between 20° and 40°, and the amount of the outgoing red light (R), which has so far appeared to be too large when the projected image is viewed from an angle between −20° and −40°. As a result, the balance between those parts in which the amount of light is too large and those parts in which the amount of light is small is improved, and the color shift can thus be reduced. Moreover, it is possible to eliminate the reversion of color of the projected light (red light (R) and blue light (B)) that occurs when the projected image is viewed from an angle of ±40° or more.

Problems solved by technology

For this reason, it has been getting difficult to reduce the color shift by the color-shift-reducing techniques proposed so far in the above-described patent publications, etc., and the situation has been changing to that these conventional techniques cannot always satisfactorily fulfill the demand for color-shift reduction.

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